Management of patients with chronic disease consumes a significant proportion of the total health care expenditure in the United States. Many of these diseases are widely prevalent and have significant annual incidences as well. Heart Failure prevalence alone is estimated at over 5.5 million patients in 2000 with incidence rates of over half a million additional patients annually, resulting in a total health care burden in excess of $20 billion. Heart Failure, like many other chronic diseases such as Asthma, Chronic Obstructive Pulmonary Disease (“COPD”), Chronic Pain, and Epilepsy is event driven, where acute de-compensations result in hospitalization. In addition to causing considerable physical and emotional trauma to the patient and family, event driven hospitalizations consume a majority of the total health care expenditure allocated to the treatment of heart failure.
An interesting fact about the treatment of acute de-compensation is that hospitalization and treatment occurs after the event (de-compensation) has happened. However, most Heart Failure patients exhibit prior non-traumatic symptoms, such as steady weight gain, in the weeks or days prior to the de-compensation. If the attending physician is made aware of these symptoms, it is possible to intervene before the event, at substantially less cost to the patient and the health care system. Intervention is usually in the form of a re-titration of the patient's drug cocktail, reinforcement of the patient's compliance with the prescribed drug regimen, or acute changes to the patient's diet and exercise regimens. Such intervention is usually effective in preventing the de-compensation episode and thus avoiding hospitalization.
In order to provide early detection of symptoms that may signal an increased likelihood of a traumatic medical event, patients may receive implantable medical devices that have the ability to measure various body characteristics. For instance, implantable devices are currently available that provide direct measurement of electrical cardiac activity, physical motion, temperature, and other clinical parameters. The data collected by these devices is typically retrieved from the device through interrogation. Alternatively, some implantable medical devices communicate with a repeater located in the patient's home via a short range wireless communications link. While the use of a repeater is convenient for a patient while located near the repeater, no data can be transmitted from the implanted device to the repeater if the implanted device is out of range. This can be extremely inconvenient, and even dangerous, for the patient if a medically significant event occurs while the implanted device is out of range of the repeater. While implantable medical devices having longer-range communications capabilities have been envisioned, these devices have typically been impracticable due to very short battery life.
Patients that have experienced traumatic medical events or that are at high risk of experiencing such events may receive implantable medical devices that can provide therapy. For instance, patients with chronic heart disease can receive implantable cardiac devices such as pacemakers, implantable cardioverter defibrillators (“ICDs”), and HF cardiac resynchronization therapy (“CRT”) devices. Typically, Electrophysiologists require their patients to make clinic visits periodically, usually once every three or four months, in order to verify that the implanted device is working correctly and programmed optimally. While some Electrophysiologists welcome this opportunity to perform certain patient specific checks, the vast majority of them require such office visit mainly to perform a device follow-up. This device follow-up is performed regardless of whether any difficulty with the device has been observed. In-person device follow-ups are not popular with Electrophysiologists because theses visits are labor intensive.
Systems have been developed that eliminate the need for in-person device follow-up visits. For instance, trans-telephonic monitoring systems have been developed for wirelessly interrogating the implanted device and transmitting device status information to a remotely located physician via a telephone line. While these systems do not require the patient and the physician to be physically proximate to one another, these systems do require that the patient and the physician be present for the device follow-up at the same time. Moreover, these systems also require that the patient be proximate to the monitoring equipment in order to perform the follow-up. If the patient is away from the location of their monitoring equipment, the remote follow-up is not possible.
Therefore, in light of the above, there is a need for an implantable medical device that has long-range wireless capabilities and that has energy management features that extend battery life to an acceptable level. There is a further need for an implantable medical device that can transmit device status data in a manner that does not require a physician to be present, and that does not require the patient to be proximate to special monitoring equipment, when the status data is transmitted.